This application is related to Japanese Patent Applications Nos. 2000-222511 filed in Jul. 24, 2000 and 2001-194838 filed in Jun. 27, 2001, whose priorities are claimed under 35 USC xc2xa7119, the disclosures of which are incorporated by reference in their entirety.
1. Field of the Invention
The present invention relates to a particle analyzer for classifying particles (for example, blood cells) in a liquid sample and measuring and analyzing the number and characteristics thereof.
2. Description of the Related Art
A conventional particle analyzer serves to electrically or optically measure parameters representing characteristics of particles in a blood sample such as erythrocytes, leukocytes or blood platelets, to create a two-dimensional scattergram based on the parameters thus obtained and to classify the particles and count the number of the classified particles. There have been known various methods of carrying out the classification on the assumption that the particles on the scattergram are normally distributed in all directions to form a cluster. For example, Japanese Unexamined Patent Publication No. Hei 5(1993)-149863 has disclosed a method of setting a fixed region in which particles belonging to a cluster will inevitably appear based on previously obtained information, obtaining an initial center-of-gravity position in the fixed region and calculating a degree of reversion to the cluster of each particle outside the fixed region and a weighted center-of-gravity position, thereby determining whether the particle belongs to the cluster. In this method, the particles close to two clusters can be allocated to each cluster. In case the separation between the clusters is poor, therefore, this method is effective. Moreover, the position of a center of gravity of each cluster and the spread of distribution are calculated. Therefore, it is also possible to detect a cluster having an abnormal pattern.
However, some kinds of particles are not always distributed normally in all directions to form a cluster. For example, a certain kind of cells sometimes have a larger size than a general size thereof although such cells have a low frequency. In such a case, there is such a distribution that most of the particles are collected in the vicinity of the center of gravity of the cluster, while the remaining particles are distributed in a position which is very far from the center of gravity in a specific direction. An example is shown in FIG. 14. FIG. 14 shows a state in which a certain kind of particles are distributed over the scattergram. It is apparent that most of the particles are distributed in the vicinity of a center G of gravity in FIG. 14, while the remaining particles are spread in the upward right direction of the center of gravity. If this kind of particles are classified by a conventional method, the cluster region should be expanded into a region in which the particles are not present. Consequently, it is hard to accurately determine the cluster.
Moreover, one of the two parameters creating a two-dimensional scattergram often fluctuates depending on the type of sample or a preservation condition of the sample. In this case, the conventional method calculates the position of the center of gravity of each cluster and the spread of distribution on the premise that an inclination of the distribution of each cluster is constant. Therefore, it is difficult to cope with a fluctuation in the inclination of the distribution of the cluster, and the accurate classification is hindered.
The present invention has been made in consideration of such circumstances and has an object to provide a particle analyzer capable of calculating a classifying line corresponding to a particle distribution state over a scattergram and counting, with high precision, particles which are not normally distributed, and a particle classifying method thereof.
The present invention provides a particle analyzer comprising a detecting section for detecting at least two kinds of parameters from a plurality of particles included in a sample, the two kinds of parameters representing characteristics of each particle, a processing section for processing the parameters detected by the detecting section; and an output section for outputting a result processed by the processing section, wherein the processing section includes a distribution chart creating section for creating a scattergram of the particles based on the detected parameters, a region setting section for presetting a particle distribution region in the created scattergram, and a classifying section for calculating a classifying line corresponding to a particle distribution state in the preset particle distribution region and for classifying the particles on the scattergram by the calculated classifying line.
Moreover, the present invention provides a particle classifying method which is carried out by the above analyzer, the method comprising the steps of detecting at least two kinds of parameters from a plurality of particles included in a sample, the two kinds of parameters representing characteristics of each particle, creating a scattergram based on the detected parameters, obtaining a variance-covariance matrix xcexa3 of the particles distributed in a predetermined particle distribution region in the scattergram and an eigenvector of xcexa3 and an eigenvalue of xcexa3, calculating a classifying line from the eigenvector and eigenvalue of xcexa3, and classifying the particles on the scattergram by the calculated classifying line.